PROJECT SUMMARY There is an increasing public concern about monitoring water quality in the entire drinking water supply system, especially at the point of use, spurred by recent water catastrophes, such as the one in Flint, Michigan that has caused severe health issues for thousands of children due to the unsafe level of lead in contaminated drinking water. Current quantitative detection methods for aqueous lead are often laboratory-based and are too expensive and time-consuming, unsuitable for end water users to perform fast and onsite detection. This project aims to investigate the feasibility of a handheld device for real-time, onsite detection of toxic lead in tap water. The device integrates a novel micro-sized sensor chip built upon a graphene-gold nanoparticle sensing platform with a portable digital signal meter for direct readout of testing results. This project intends to address the need for quantitative, real-time, in situ detection of total dissolved lead ions in tap water by developing a sensitive, specific, fast, portable, and cost-effective prototype handheld device that can be self-administered without any special training. Major innovations of the project lie in the use of an aqueous sensing platform with superior sensing performance (i.e., high sensitivity, excellent selectivity, and fast response under laboratory environment and in field settings) and the combination of the sensor with a digital meter for direct display of testing results in tens of seconds. The sensing platform consists of a multifunctional hybrid nanostructure (i.e., graphene as the sensing signal transduction channel and the support for gold nanoparticles functionalized with chemical probes), which is capable of differentiating lead ions from other aqueous ions (e.g., calcium and magnesium) through specific coupling events between the lead ion and the specially chosen chemical probe (i.e., glutathione) on the gold nanoparticle surface. Specific research aims of the project are to: (1) Determine the influence of pH value on the sensor performance so that sensing results can be interpreted properly; (2) Develop a model to estimate the total dissolved lead based on the measurement of free lead ion concentration in water and implement this model in the handheld device for reporting total dissolved lead concentration in water; (3) Study how potential interfering species in tap water (e.g., disinfection by-products) affect the sensing behavior of the handheld device and to identify possible strategies to minimize the undesirable interference. The technical and commercial feasibility of the handheld device and associated technology will be determined for future development and commercialization. The proposed activities will improve the sensing reliability and device integrity, maximizing the commercialization opportunities of the device. The availability of the device contributes to safeguarding the public drinking water safety, as this innovative sensing technology permits fast, onsite test of lead ions in water supply systems, particularly at the point of use. The framework of the device is also expandable with the potential to serve as the basis to build a sensing network for real-time water quality monitoring of the entire drinking water system, enhancing the public drinking water safety.